The best strategy I've heard for podcasts is actually cross-pollination. You see this a lot where podcasters will go on each other's shows to guest host and show support. It helps raise awareness of different podcasts and boost discovery.

Also - live podcast tapings and festivals! They are such great ways to find podcasts.

Last - recommendations from friends. That is how I found out about Teen Creeps, for instance, a comedy podcast about YA fiction from the 80s and 90s.